Add initial test files from lodash v4. (#4172)

* Install test dependencies.

* Add initial test files.

These files were created using a simplistic AST manipulator using `recast` to
preserve formatting. There's bound to be a huge chunk of errors, but this serves
as a good start. QUnit was replaced with Mocha, with ES2015 imports running via
`esm`.

As far as possible, QUnit-specific syntax has been replaced with Mocha's
`describe` and `it`, while the native Node.js `assert` module is used for
assertions. Files in the `test` directory ending in `.test.js` will be treated
as test files.

* Add initial passing files to test run.

test/without.test.js

@@ -0,0 +1,23 @@
+import assert from 'assert';
+import without from '../without.js';
+
+describe('without', function() {
+  it('should return the difference of values', function() {
+    var actual = without([2, 1, 2, 3], 1, 2);
+    assert.deepStrictEqual(actual, [3]);
+  });
+
+  it('should use strict equality to determine the values to reject', function() {
+    var object1 = { 'a': 1 },
+        object2 = { 'b': 2 },
+        array = [object1, object2];
+
+    assert.deepStrictEqual(without(array, { 'a': 1 }), array);
+    assert.deepStrictEqual(without(array, object1), [object2]);
+  });
+
+  it('should remove all occurrences of each value from an array', function() {
+    var array = [1, 2, 3, 1, 2, 3];
+    assert.deepStrictEqual(without(array, 1, 2), [3, 3]);
+  });
+});